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 Subject: Joining cubes and spheres/cylinders - have I done this sensibly?

3dcheapskate opened this issue on May 13, 2010 · 44 posts

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  3dcheapskate    ( ) ( posted at 2:58AM Thu, 13 May 2010 


I'm currently tidying up a model of a Tibetan-style stupa and I'd like to clear up a couple of things before I release it (as a freebie later this month).

I'm very much a beginner at 3D modelling, and this is a fairly basic model (just over 1000 vertices/1000 faces). It was created from a few spheres, cubes and cylinders, which were then extruded, manipulated, and finally joined together.

The way I joined things was fairly laborious, creating edges and faces one by one to fill the gap between the 4-sided and 16-sided elements - any advice on a smarter way to do this?

I think that the end result (i.e. the actual quads and triangles that fill the join area) is okay - it looks 'neat and tidy', and it renders okay in D|S 3 and Poser 6 (well, not quite).

However, I may have made some very basic errors in constructing these joining areas. Any advice/suggestions would be greatly appreciated.

(Hopefully there's a  picture attached to this posting which shows exactly what I mean)

3D Cheapskate

Pete Williams (aka the 3DCheapskate) still posts stupid stuff at all the usual places



  EnglishBob    ( ) ( posted at 4:44AM Thu, 13 May 2010  · @3643957

There are neater ways, but the proof is in the rendering, I suppose. What problems are you having in Poser?

The other question has to be, do you even need to join them like that? It's quite legitimate to just shove primitives together, although I can understand how you would want to be proud of your craftsmanship before releasing something. :-) 


  3dcheapskate    ( ) ( posted at 6:34AM Thu, 13 May 2010  · @3643991


A picture speaks a thousand words, so here are DS3 and P6 renders with crease/smoothing angles of 45 and 89 degrees - DS3 with 45 degs seems fine to me. P6 seems to have some flat grey faces.

You mention "neater ways" - any good links? Don't just leave me hanging here with that tantalising hint!

I started this model by *"Just shoving primitives together"*h - the crescent, sphere and teardrop on top are left that way since I reckoned (a) it was too much effort and (b) hey, nobody would notice up there!

I guess that if you know how to do things properly, then sloppy work is a matter of personal choice, not necessity!   ;o)

Pete Williams (aka the 3DCheapskate) still posts stupid stuff at all the usual places



  EnglishBob    ( ) ( posted at 8:04AM Thu, 13 May 2010  · @3644029

Attached Link: http://blenderartists.org/forum/showthread.php?t=93651

Neater ways... Let me see... It's hard to explain in words, and it would take a lot of pictures. The linked tutorial is for organic modelling, and it's for Blender but a lot of the principles hold true anywhere and it may be a good introduction.

What you have here looks like the good old Poser sharp edges problem, and you probably know this since you've been experimenting with the smoothing angle. I'm not saying that's wrong, but being an old timer I tend to stick with the old fashioned way, which is to split the edges that you want to be sharp. I do that in UVMapper Pro - what do you have available, modelling-wise?

The other option is to run a very fine bevel along the sharp edges. The basic principle is that Poser is biased towards rendering rounded forms, i.e. figures, so you have to work hard to persuade it that you really do want a sharp edge between those surfaces.


  airflamesred    ( ) ( posted at 4:19PM Thu, 13 May 2010  · @3644401

I don't have a link but 'edge flow' would be the key to doing a really great job. This would lose the tri's. For a freebie it looks perfectly fine. As for the smoothing is it not optional?


  ShawnDriscoll    ( ) ( posted at 10:22PM Thu, 13 May 2010  · @3644505

I use 50 degrees for my creasing.  Also check your normals.

www.youtube.com/user/ShawnDriscollCG


  3dcheapskate    ( ) ( posted at 11:24PM Thu, 13 May 2010  · @3644517


It's the areas highlighted in red on the new image attached to this post which don't look right to me in Poser. Maybe it's not the model at all, but something to do with the lighting? I used the default lighting setups in both DS3 (1 light) and P6 (3 lights) - maybe I need to go away and experiment a bit?

The sharp edges (marked in green on the new image here) aren't my major concern, but I appreciate the comments:

  • I can see how adding a bevel would improve the appearance, make it look more natural - might try that.
  • I've set "creaseAngle 45" in the .pp2.  Agreed, the DS/Poser end user can play around with the crease/smoothing parameters, but it looks more professional if the default settings work. (I noticed that DS3 seems to set smoothing angle to 89.9 degrees, ignoring the creaseAngle in the .pp2?)

Pete Williams (aka the 3DCheapskate) still posts stupid stuff at all the usual places



  3dcheapskate    ( ) ( posted at 11:33PM Thu, 13 May 2010  · @3644518

"Check your normals" - sound advice! I got caught by that one very early on, so I now usually recalculate normals before saving my work / exporting my .obj. Having said that, those problem faces on the Poser render could be inverted normals - I'll feel rather foolish if that's the case, better go and check!

Pete Williams (aka the 3DCheapskate) still posts stupid stuff at all the usual places



  ShawnDriscoll    ( ) ( posted at 12:04AM Fri, 14 May 2010  · @3644528

Quote - I can see how adding a bevel would improve the appearance, make it look more natural

And you don't have to tell Poser about any creasing/smoothing also.

www.youtube.com/user/ShawnDriscollCG


  ShawnDriscoll    ( ) ( posted at 12:07AM Fri, 14 May 2010 · edited on 12:08AM Fri, 14 May 2010 · @3644529

Quote - "Check your normals" - sound advice! I got caught by that one very early on, so I now usually recalculate normals before saving my work / exporting my .obj. Having said that, those problem faces on the Poser render could be inverted normals - I'll feel rather foolish if that's the case, better go and check!

What does the shading look like for those areas if you remove the image texture from the object?  Could be a mapping problem.  Or even duplicate polygons on top of each other (rare though).

www.youtube.com/user/ShawnDriscollCG


  3dcheapskate    ( ) ( posted at 12:11AM Fri, 14 May 2010  · @3644532

Back to those "neater ways". I think that I understand the basic principles of edge loops, etc, but applying them in a practical situation is another matter!

EnglishBob: that link's great (you won't remember, but you sent me there in November last year from the "WIP-Modeling a Bellydance Costume Grp. Project" thread over on the DAZ forums).

Following on from that I've looked at lots of stuff about poles, edge loops, quads and triangles. I think I understand the basic principles. One of the simplest, most enlightening things I read was this one, Keep it simple. Four verts good, three verts bad...usually, and it's the advice I try to follow.

However, I spent a long time trying to use quads to join the square parts of this model to the rounded parts. But every approach I tried seemed to add unnecessary complexity to the model. That's why I went with the triangles.

But I'm intrigued - it must be possible to do with quads?

Pete Williams (aka the 3DCheapskate) still posts stupid stuff at all the usual places



  ShawnDriscoll    ( ) ( posted at 1:30AM Fri, 14 May 2010 · edited on 1:33AM Fri, 14 May 2010 · @3644559

Quote - But I'm intrigued - it must be possible to do with quads?

Yes.  The trade-off is a denser mesh, which is a dream for someone with OCD.  Triangles are fine for tight areas even if smoothing your model (since smoothed triangles are converted to quads anyway).  It's the n-gons that can cause more problems actually.  Where n > 4 sides.

www.youtube.com/user/ShawnDriscollCG


  3dcheapskate    ( ) ( posted at 2:29AM Fri, 14 May 2010  · @3644574


Thanks Shawn, I've just done a bit of checking:

  • I'm fairly sure it's not duplicate polygons. I checked in Blender - no duplicate vertices.
  • In Poser, looking around with the viewpoint inside the model doesn't show up any back-to-front faces, so I don't think it's the normals.
  • It's not an effect of the Poser default lights. I removed all but one, and moved that around. Those faces look wrong regardless of where the light is.
  • I also did a render without textures - exactly the same effect. So I guess it's not the mapping either

But I did notice that the problem only appears at three of the four corners where the cube intersects the dome. I know that the geometry at each of the four corners is slightly different, as I did each by hand. I guess that's a definite clue? But I don't see where it's pointing me!

Pete Williams (aka the 3DCheapskate) still posts stupid stuff at all the usual places



  EnglishBob    ( ) ( posted at 4:07AM Fri, 14 May 2010 · edited on 4:07AM Fri, 14 May 2010 · @3644597

"The sharp edges (marked in green on the new image here) aren't my major concern, but I appreciate the comments"

I'm not sure if you've fully appreciated what Shawn and I were saying, so forgive me if I'm repeating myself unnecessarily. The very fact that your model has sharp edges can cause Poser to render it improperly.

As well as your concern for the aesthetics of the mesh, there's a separate issue when you consider modelling for Poser. Sharp edges have to be given special treatment, as mentioned. There are also issues with long, thin triangles (Poser doesn't like them) and polygons with more than 4 sides (Poser sometimes likes them, but they're best avoided - and concave n-gons are definitely not a good idea). And probably other things that I've temporarily forgotten about.

"the problem only appears at three of the four corners where the cube intersects the dome. I know that the geometry at each of the four corners is slightly different, as I did each by hand."

That is a clue, certainly. If the mesh was mine, I'd look very closely indeed at how the polygons are formed in the corners; make sure that all vertices were welded prior to splitting them; and check for malformed polygons (UVMapper has functions for that). If you're willing to send me the model, I could have a quick look and give any feedback here.

"you won't remember, but you sent me there in November last year from the "WIP-Modeling a Bellydance Costume Grp. Project" thread over on the DAZ forums)"

I remember the thread, and I remember your screen name. Is that good enough? ;-) I just hadn't connected the two.


  3dcheapskate    ( ) ( posted at 4:24AM Fri, 14 May 2010  · @3644600


I was almost there with the quads!  I've just looked back at my notes, done a bit of fiddling around, and came up with this. It still seems a bit like overkill for my current model, but I can see that it might be right for an organic model.

Pete Williams (aka the 3DCheapskate) still posts stupid stuff at all the usual places



  3dcheapskate    ( ) ( posted at 5:09AM Fri, 14 May 2010 · edited on 5:09AM Fri, 14 May 2010 · @3644624

The penny drops! Poser doesn't like sharp edges.

You mention splitting the edges as an alternative to using a bevel. I'm not sure of the terminology, but are you talking about material groups here? I haven't really got my head round those yet. I use Blender for the modelling and UV mapping, although I still load the .obj file into UV Mapper (free version) just to export the texture template!? Go figure!

I'd already come across the long, thin triangles problem (there's a few still in this model where the square plinth changes to the rounded, stepped affair), and I guess that was part of the reason for this particular post.
I was also vaguely aware of an N-gons issue - I've only used quads and triangles in my practice models because I vaguely recalled some warning about faces with 5+ sides.
The concave N-gon issue - that applies to concave quads as well, doesn't it?

Thanks for the offer - I'd be more than happy for you to give the model a once-over. What's the best way? Send a file to the contact address on your website. Which file? I think Blender can export most formats, or would just the .obj be enough?

It's been a long time since that first post , but I have been making slow but steady progress! Hopefully, one day I'll get back to the clothing - I just realised I had far, far too much to learn!

Pete Williams (aka the 3DCheapskate) still posts stupid stuff at all the usual places



  EnglishBob    ( ) ( posted at 6:00AM Fri, 14 May 2010  · @3644631

Quote - You mention splitting the edges as an alternative to using a bevel. I'm not sure of the terminology, but are you talking about material groups here?

Not material groups, no.

Imagine two flat planes, one horizontal and one vertical, which share an edge to make a right angle. Further imagine that the edge in question is made of a string of vertices, which are shared between the vertical and horizontal planes. Poser will assume that both planes are part of the same surface and try to smooth them according to its own internal algorithms (now somewhat controllable by the smoothing angle setting, but still...)

If each vertex along the edge is duplicated, so that there are separate vertices for the vertical and horizontal planes, Poser now "knows" that the surfaces must be kept separate and doesn't attempt to smooth the edge.

This process is often known as "splitting vertices". UVMapper Classic has a function for this, but it actually splits all the vertices in the model which is not what you want if it has any curved surfaces at all. UVMapper Pro enables you to set the angle which will trigger the splitting, along with other useful features.

Quote - I vaguely recalled some warning about faces with 5+ sides.

That was probably my vague warning. :-) Poser 3 used to actually crash if it as much as thought it was going to get a 5-sided polygon. Later versions are more robust, but the suspicion lingers that they are best avoided.

Quote - The concave N-gon issue - that applies to concave quads as well, doesn't it?

Well spotted, grasshopper. :-)

Quote - Send a file to the contact address on your website. Which file? I think Blender can export most formats, or would just the .obj be enough?

Yep, just send the OBJ file to my contact address and I'll take a quick look.


  EnglishBob    ( ) ( posted at 7:39AM Fri, 14 May 2010  · @3644650


Interesting. Splitting vertices certainly helps - but it doesn't deal with those triangles. Here's a wipe between renders of the two meshes.

More research is needed... :-) 


  3dcheapskate    ( ) ( posted at 11:48AM Fri, 14 May 2010 · edited on 11:50AM Fri, 14 May 2010 · @3644703


Those remaining triangles reminded me of something, and I eventually tracked it down - a simple shaded view (that's the picture included with this post) in Blender looks a bit odd directly above those triangles. Maybe a complete red herring though.

I hadn't even thought of just importing the .obj. It gives a rather different result from loading via the .pp2. Does that hint that there's something wrong in the .pp2 as well - it wouldn't surprise me!   :oS

Regarding the sharp edges: I assume that it's an either/or choice - either split the vertices, or bevel the edges?

Time to go and rest my brain for a while - thanks to everybody for the advice so far

Pete Williams (aka the 3DCheapskate) still posts stupid stuff at all the usual places



  EnglishBob    ( ) ( posted at 1:24PM Sat, 15 May 2010  · @3645085

Quote - Those remaining triangles reminded me of something, and I eventually tracked it down - a simple shaded view (that's the picture included with this post) in Blender looks a bit odd directly above those triangles.

The artifacts in the non-split vertices model tend to occur in the same places in Poser, although they don't look the same.

Quote - I hadn't even thought of just importing the .obj. It gives a rather different result from loading via the .pp2. Does that hint that there's something wrong in the .pp2 as well - it wouldn't surprise me!

The PP2 file will include whatever smoothing angle you had in force when you saved it, and that will have an influence on how it looks.

Quote - Regarding the sharp edges: I assume that it's an either/or choice - either split the vertices, or bevel the edges?

You can treat edges differently, if you like. Bevel some, split others - not sure what benefit that might have. You can even do both, but that definitely would be pointless.

I haven't had a chance to get back to this yet. I suspect the answer may be some ad hoc modification that fixes the problem although it will be hard to explain why...


  3dcheapskate    ( ) ( posted at 11:39PM Sun, 16 May 2010 · edited on 11:42PM Sun, 16 May 2010 · @3645698


Got it! The Poser render problem turned out to be smoothing groups in the .obj file (basic .obj format here http://en.wikipedia.org/wiki/Obj ). Smooth shading was set in the .obj for about twenty faces (some triangles, some quads) - somehow I must have told Blender to do this. One of the risks of using a tool you don't fully understand, I guess?!

Here's an extract from the .obj - it might help anybody who has a similar problem:

usemtl Stupa
s off
f 30/1 34/2 49/3 31/4
...
s 1
f 18/695 21/694 451/584
s off
...

Simply removing all the "s 1" / "s off" line pairs (but not the faces between them!) cleared the problem.

Pete Williams (aka the 3DCheapskate) still posts stupid stuff at all the usual places



  3dcheapskate    ( ) ( posted at 2:20AM Mon, 17 May 2010 · edited on 2:28AM Mon, 17 May 2010 · @3645733


The biggest clue was when I started cutting off bits of the model. Even when all I had left was just the curved top of the dome those pesky triangles were still there. At that point I opened the .obj file and spotted it.

Time to go and tidy up those sharp edges now. Maybe also increase the number of segments on the rounded bits to give it a smoother outline.

Thanks again to everybody who's posted replies here. This has been a most enlightening experience for me.

I'll probably repost here in a week or two, just for a final check before releasing the model (or if I run into any other major problems!)

Pete Williams (aka the 3DCheapskate) still posts stupid stuff at all the usual places



  EnglishBob    ( ) ( posted at 8:10AM Mon, 17 May 2010  · @3645808

Aha! I never thought to check for smoothing groups. It isn't usually an issue for me - I think some part of my usual workflow normally strips them out. Glad you got it sorted out, anyway. 


  markschum    ( ) ( posted at 11:29PM Tue, 18 May 2010  · @3646507

Poser seems to recognise smoothing groups if you can set them up in your modelling program.

Poser will only smooth an edge if the vertices are welded. Rather than split vertices in uvmapper, you can select polygons where you want a sharp edge and simply cut and paste them back, or by selecting the vertices of the edge and unweld. You need to know your modeller to learn exactly what the command is called. 

N-gons in poser, especially with a concave edge are fatal in poser. a single polygon shaped like a crescent will not render properly in poser.


  3dcheapskate    ( ) ( posted at 5:55AM Thu, 20 May 2010 · edited on 6:02AM Thu, 20 May 2010 · @3647024


Okay, not quite there yet. But after playing around with some subdivision, sliding edge loops/vertices, and bevels, I think some light bulbs are glowing dimly in my brain.
The new version of the dome with the square bit on top just looks so much better too me. And hey, who'd have guessed? Edge loops just seemed to appear! I think (and I'm often wrong, but maybe not this time) that the edge loops make sense too!

I've added regular exports of parts of my model as obj for examination in DS and Poser to my workflow. Yes,  I know it's obvious now!

I'm a little unsure about the triangle that appears in the bevel, where the dome and square corner meets (in the blue circle on the diagram). But I think that seems to be a triangle in its proper place.

Talking of bevels, I noticed that I can make the corner bevels on the base out of quads or triangles (the two images on the right). Is there any reason I should prefer one over the other?

Any views/observations on any of this?

P.S. thanks markschum. I think I'm going with bevels on this model, but I'll check out the commands you suggested - I'm playing with Anim8or now as well as Blender.

Pete Williams (aka the 3DCheapskate) still posts stupid stuff at all the usual places



  3dcheapskate    ( ) ( posted at 11:19AM Fri, 28 May 2010  · @3650531


Okay, almost there - I should be ready to release in the next day or two. I now have my basic  texture/bump maps, a .pp2 file, and .pz2 MAT pose files. I also have .mc6 equivalents for Poser 6+.

Everything seems fine in Poser 6 - see the attached render.

But D|S is giving me a problem with the bump map. It sets the bump strength correctly, but not the min/max values.

I read somewhere that D|S ignores the shader tree, which would explain this.

Is there any other way I can get D|S to set the bump min/max automatically when I load the prop?

Pete Williams (aka the 3DCheapskate) still posts stupid stuff at all the usual places



  airflamesred    ( ) ( posted at 2:59PM Fri, 28 May 2010  · @3650617

The specularity looks a bit high to me (on this render) but the mesh looks great

Awfull lot of work - lets hope folks D/L it

best of luck


  3dcheapskate    ( ) ( posted at 8:57PM Fri, 28 May 2010  · @3650704

"...specularity looks a bit high..." - I think you're right there. The bump detail's getting lost. I'll try reducing it a bit.

"Awfull lot of work" - Yes indeed, but mainly for my own benefit! I've learnt so much over the past few weeks while tidying up this model.

Pete Williams (aka the 3DCheapskate) still posts stupid stuff at all the usual places



  3dcheapskate    ( ) ( posted at 10:23AM Sun, 30 May 2010  · @3651483

It's up on ShareCG now. Just need to check that the download is all okay, then I'll add posts in the freebies sections.

Pete Williams (aka the 3DCheapskate) still posts stupid stuff at all the usual places



  3dcheapskate    ( ) ( posted at 10:00PM Sun, 30 May 2010 · edited on 10:02PM Sun, 30 May 2010 · @3651850

Also now appearing on Renderosity freestuff.

See my thread in the freestuff forum here http://www.renderosity.com/mod/forumpro/showthread.php?thread_id=2803020

Pete Williams (aka the 3DCheapskate) still posts stupid stuff at all the usual places



  MidnightCarnival    ( ) ( posted at 11:28PM Sun, 30 May 2010  · @3651909

 Forgive me because I'm completely novice and new but that looks like a huge frustration - especially having to get into making illustrations to demonstrate the problem.

With freeware programs like Sculptris and CB Model where everything can be easily molded and glued together are primitive-based modeling programs still practical?

I have a few freeware primitive based programs but hang onto them as more of a 'fun challenge' to learn. Starting off, I'm learning with the above-mentioned clay-style programs because it seems so much more quicker.

But once again, I'm pretty new, what advantages are there in toughing it out with the more complicated to use programs?


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